1. Field of the Invention
The present invention relates to an imaging method and microscope device.
Priority is claimed on Japanese Patent Application No. 2010-215906, filed Sep. 27, 2010, the content of which is incorporated herein by reference.
2. Description of the Related Art
All patents, patent applications, patent publications, scientific articles, and the like, which will hereinafter be cited or identified in the present application, will hereby be incorporated by reference in their entirety in order to describe more fully the state of the art to which the present invention pertains.
In recent years, virtual microscopes have become widely known in fields of pathology such as cell and tissue diagnosis. These microscopes take a color photograph of an entire sample on a glass slide on which a test specimen has been placed, and then convert this photograph into a digital image. This is then displayed on a monitor, and can be manipulated just as if the test specimen were being observed using an actual microscope. Moreover, because accurate diagnoses are required in medical images that are used for pathological cell and tissue diagnosis, there is a need for the color of the subject to be accurately reproduced.
One method which is known to improve the color reproducibility of a photographic image is a method in which, using RGB color image data for the subject and point-measured spectrum information (i.e., a point-measurement spectrum) for the subject, the estimation accuracy of the spectral reflectance of a 3-band RGB image is improved, so that the color reproducibility of a color image of the sample slide is improved (see, for example, “Experimental evaluation of color image estimation method using multipoint spectrum measurements” by Tokyo Institute of Technology, Imaging Science and Engineering Laboratory, K. Ietomi et al., Proceedings of the 54th Spring Meeting, JSAP and Related Societies, 2007 Spring, which is hereinafter referred as Non-patent document 1, and “Piecewise Wiener estimation for spectrum-based color reproduction using multipoint spectral measurements” by Tokyo Institute of Technology, Imaging Science and Engineering Laboratory, Y. Murakami et al., Proceedings of the 55th Spring Meeting, JSAP and Related Societies, 2008 Spring, which is hereinafter referred as Non-patent document 2). In addition, a method in which a spectrum detector such as a spectrometer is used is widely known as a method for acquiring a point-measurement spectrum.
FIG. 24 is a block diagram illustrating a structure of a microscope device which has been fitted with a spectrum detector in accordance with the related art. A microscope device 1400 shown in the drawing includes a stage 1402 on which a test specimen 1401 is placed, and with a stage drive unit 1403 that moves the stage 1402 in a horizontal direction and in the direction of the optical axis. The microscope device 1400 also includes a light source 1404 that illuminates the test specimen 1401, a condenser lens 1405 that condenses light from the light source 1404, an objective lens 1406 that is formed by a plurality of lenses in such a manner that it faces the test specimen 1401, a first imaging lens 1407 that is located on the optical axis of the objective lens 1406, and a camera 1408 that photographs an image of the test specimen 1401.
The microscope device 1400 also includes an AF unit 1409 that creates a focusing signal which is required to focus an image of the test specimen 1401 in the camera 1408, and with a spectrum detector 1410 that acquires spectrum information about a predetermined portion of the test specimen 1401. The microscope device 1400 also includes a beam splitter 1411 and a beam splitter 1412 that are located on the optical axis of the objective lens 1406 and that divide the light from the test specimen 1401 and guide it towards the AF unit 1409 and the spectrum detector 1410. The microscope device 1400 also includes a condenser lens 1413 that condenses light from the beam splitter 1411 and guides it towards the AF unit 1409. The microscope device also includes a condenser lens 1414 that condenses light from the beam splitter 1412 and guides it towards the spectrum detector 1410. The microscope device 1400 also includes an image processing section 1415 that, based on spectrum information detected by the spectrum detector 1409, corrects images acquired by the camera 1408.
Next, the method used by the microscope device 1400 to acquire images of the test specimen 1401 will be described. Firstly, the stage drive unit 1403 drives the stage 1402 in a horizontal direction, and moves a predetermined photograph area of the test specimen 1401 which has been placed on the stage 1402 to within the field of view of the camera 1408. Next, based on commands from the AF unit 1410, the stage drive unit 1403 moves the stage 1402 in the optical axis direction such that an image of the test specimen 1401 is formed on an image sensor surface of the camera 1408.
Next, after the image of the test specimen 1401 has been formed on the image sensor surface of the camera 1408, the camera 1408 acquires an image of a predetermined photograph area of the test specimen 1401, and the spectrum detector 1409 detects the spectrum of this predetermined area of the test specimen 1401. Next, based on the spectrum information detected by the spectrum detector 1409, the image processing section 1415 corrects the image acquired by the camera 1408 so that the color reproducibility of the acquired image of the test specimen 1401 is improved.
In this manner, a microscope device 1400 is known that splits light from the test specimen 1401 and guides the light to the camera 1408, the AF unit 1410, and the spectrum detector 1409 (see, for example, Japanese Unexamined Patent Application, First Publication No. 2008-209627).
The above described spectrum detector 1409 creates spectrum information that is used to improve the color reproducibility of the image of the test specimen 1401 that was acquired by the camera 1408 and, in order for the color of the image of the test specimen 1401 to be reproduced with a high degree of accuracy, it is necessary for a sufficient quantity of light to be irradiated onto the spectrum detector 1409 so that highly accurate spectrum information can be created. The AF unit 1410 creates focusing signals that are used to focus the focal point of the camera 1408 and, in order for highly accurate focusing to be performed, it is necessary for a sufficient quantity of light to be irradiated onto a light detecting element (not shown) inside the AF unit 1410.
However, in the imaging method employed by the conventional microscope device 1400, light from the test specimen 1401 is split three-ways by the beam splitter 1411 and the beam splitter 1412, and the light which has been split three-ways is irradiated onto each one of the camera 1408, the AF unit 1410, and the spectrum detector 1409 so that image acquisition of the test specimen, creation of a focusing signal, and creation of spectrum information are performed. In this manner, in the conventional microscope device 1400, because the light from the test specimen 1401 is split three-ways, it is not possible to obtain a sufficient quantity of light to create a focusing signal and to create spectrum information. As a consequence, the microscope device 1400 is not able to perform highly accurate auto-focusing, and it is not possible to achieve a satisfactory improvement in the color reproducibility of the acquired image of the test specimen 1401.